[unreadable] Over the past several years, investigators of the UCLA Integrated Substance Abuse Programs (ISAP) have built upon clinical experience gained from providing treatment for methamphetamine-dependent individuals to develop a human laboratory program aimed at assessing the neurobiological consequences of methamphetamine exposure. Current research designs at ISAP and other research groups focus on the evaluation of methamphetamine-dependent individuals following abstinence initiation. While these studies are important, they do not utilize neurocognitive impairment as a marker for determining the extent of methamphetamine-associated neurotoxicity. Because impaired neurocognitive functioning is associated with poorer functional outcomes (e.g., employment status, treatment outcome), reversal of these impairments could enhance the quality of treatments for methamphetamine dependence. We propose to explore whether a candidate medication, modafinil, can ameliorate methamphetamine associated neurocognitive impairment in non-treatment seeking methamphetamine-dependent volunteers. The data generated from this study will eventually provide valuable insights into the neurobiological mechanisms that underlie methamphetamine-associated neurocognitive impairments. Moreover, because our team collaborates with researchers at UCLA who conduct treatment outcome studies for methamphetamine-dependent individuals, the findings from the proposed work can be rapidly and practically integrated into current treatment models. [unreadable] [unreadable] [unreadable] [unreadable]